Tip on jittery or twitchy screen displays
I remember a recent post (during the final days of AFF 1.0 IIRC) in which someone did a VGA mod and said it was basically okay but the display was a bit twitchy.
I recently did my first VGA mod ( 
), and the display was fine. But then I had to disassemble the unit for something, and when I reassembled it, lo and behold the screen image was jittery.
Did some looking, and I realized that the orange connector on a wire that goes from the video board to the metal cage on the analog board was loose, almost disconnected. I'm referring to the connector that's about 1/3 from the top and 1/3 from the right in the following photo:
http://www.colourclassicfaq.com/highres/img/mac640_7.jpg
It's the connector just above the leftmost adjutment pot hole on the analog board.
Anyway, I reattached the connector, and the screen jitteriness went away.
I wanted to confirm that this connector was the cause when I had the unit on, but I was too chicken to wriggle it around with the unit powered up. 
Is this connector for some kind of grounding? Anyone know its function?
Matt
That connector is to the de-gauss cables around the CRT. Stuart
My suspicion is that although he is *holding* the de-gauss connector, what he is actually referring to is the ground wire connector from the PCB.
Sorry for the confusion, guys -- I was in a rush so I just grabbed a pic from the High-Res modification procedure in the CC FAQ. The guy in the pic -- that's not me! -- is in fact holding the degauss cable, but dead_elvis is correct: I am referring to the ground wire connector from the PCB.
Matt
!@#$% new URL link tool!
This should work:
http://www.colourclassicfaq.com/highres/img/mac640_7.jpg